410 Stainless Steel tubing offers significantly increased heat transfer and strengths, as well as a reduction in thermal expansion, when compared to typical austenitic Stainless Steel tubing grades such as 316L.
Thermal conductivity of 410 Stainless Steel tubing is 53% BETTER at the same wall thickness than 316L tubing (410 k=24.9 W/m-K; 316L k=16.3 W/m-K @ 100 degrees centigrade). Engineers will appreciate the ability to reduce the wall thickness of 410 Stainless Steel within their heat exchanger designs, while still maintaining burst pressure requirements. Overall heat transfer can be improved an additional 400% in hardened 410 designs relative to conventional heavy-wall 316L heat exchangers rated for identical maximum pressures.
Thermal stresses are also reduced as 410 has a Coefficient of Thermal Expansion (CTE = 9.9 um/m/K) 38% less than 316L (CTE = 15.9 um/m/K). As a result, thermal fatigue stresses are reduced and product durability is increased.
The introduction of 410 Martensitic Stainless Steel for the fabrication of heat exchanger tubing offers higher strength, increased hardness and wear resistance, as well as a lower cost alternative to Ferritic series Stainless Steel alloys, which include 410S.
The hardened strength of 410 Martensitic Stainless Steel is twice that of 410S. Heat exchanger tubing made out of 410 Stainless Steel will allow for thinner walled material to carry the same pressures, increasing heat transfer and making the heat exchanger much more effective. Using less material also reduces overall costs per tube, heat exchanger fabrication and shipping costs.
A shell and tube heat exchanger is just one type of heat exchanger design. It is suited for higher-pressure applications and markets such as: dairy, brewing, beverage, food processing, agriculture, pharmaceutical, bioprocessing, petroleum, petrochemical, pulp & paper, and power & energy.
As its name implies, this type of heat exchanger consists of an outer, elongated shell (large pressure vessel or housing) with a bundle of smaller diameter tubes located inside the shell housing. One type of fluid runs through the smaller diameter tubes, and another fluid flows over the tubes (throughout the shell) to transfer heat between the two fluids. The set of tubes is called a tube bundle, and may be composed of several types of tubes; round, longitudinally finned, etc. depending on the particular application and fluids involved.
There may be variations on the shell and tube design. Typically, the ends of each tube are connected to plenums or water boxes through holes in the tubesheets. The tubes may be straight or bent in the shape of a U, which are called U-tubes.
The selection of material for tubing is extremely important. To be able to transfer heat well, the tube material should have good thermal conductivity. Because heat is transferred from a hot to a cold side through tubes, there is a temperature difference through the width of the tubes. Because of the tendency of the tube material to thermally expand differently at various temperatures, thermal stresses occur during operation. This is an addition to any stress from high pressures from the fluids themselves. The tube material also should be compatible with both the shell and tube side fluids for long periods under the operating conditions (temperatures, pressure, pH, etc.) to minimize deterioration such as corrosion. All of these requirements call for careful selection of strong, thermal conductive, corrosion-resistant, high-quality tube materials. Typical metals used in the manufacturing of heat exchanger tubing include: carbon steel, stainless steel (austenitic, duplex, ferritic, precipitation-hardenable, martensitic), aluminum, copper alloy, non-ferrous copper alloy, Inconel, nickel, Hastelloy, tantalum, niobium, zirconium, and titanium.